The three major goals of this research are: (1) The elucidation of the natural history of experimental cerebral infarction by development and exploitation of adequate methods for monitoring local or regional blood flow, oxygen availability, pH, electrocorticogram, intracranial pressure, steady potential, and tissue impedance, correlating these with histopathologic and histochemical studies of the infarction; (2) Application of some of these monitoring techniques in cases of human cerebral infarction when these invasive techniques are technically feasible and ethically appropriate, being likely to benefit the individual patient. These conditions are satisfied in the cases being submitted to craniotomy for treatment of ruptured intracranial aneurysm; (3) Utilization of the information gained from the invasive monitoring techniques to evaluate and validate relatively non-invasive monitoring methods which would be more widely applicable to the common clinical problems of progressing stroke and subarachnoid hemorrhage. These methods include: 133Xenon inhalation, total jugular blood flow, cerebral A-V oxygen difference, EEG, orthodox angiography, and isotope angiography. Full realization of these goals will be facilitated by effective interaction among our developing team of physician-physiologist and basic scientist-engineers.